For example, as disclosed in Patent Document 1, as a lifter mechanism of a seat structure, a mechanism in which, when a transfer mechanism (in Patent Document 1, a mechanism configured by including an operation lever, a lever base, a lock base, a locked member, and an operation shaft) rotates from a neutral position by input torque, an output unit rotates to rotate a pinion and a sector gear connected to the output unit and lift a seat cushion, is known.
In Patent Document 1, in between the transfer mechanism and the output unit, a brake drum for transfer controlling the input torque to the output unit is interposed. The brake drum has an outer cylinder and an inner cylinder (in Patent Document 1, the inner cylinder is commonly used as the output unit connected to the pinion). In between the outer cylinder and the inner cylinder, a pair of two brake springs is installed. The inner cylinder is connected to the operation shaft composing the transfer mechanism. Each end portion of each brake spring is engaged to the inner cylinder and the pinion. When the operation shaft rotates in any direction by the input torque added to the operation lever and accordingly, the inner cylinder rotates in any direction, each brake spring acts in a reduced diameter direction to enable the inner cylinder to rotate, and transfer the force to the pinion. On the other hand, when a force that rotates the inner cylinder is imparted from the pinion or the like that is an output side, each brake spring acts in an increased diameter direction to disable the inner cylinder to rotate by contacting to an inner circumferential surface of the outer cylinder. Thereby, the operation shaft is prevented from rotating due to a load of the seat cushion side, and the seat cushion that is adjusted to a predetermined height by operation of the operation lever can maintain its position.